The Universal Disk Format (UDF) is a universal vendor-independent file system format designed for data interchange and portability. UDF allows an operating system to access (read/write/modify) data that was created by another operating system or device. UDF is a subset of, and is fully compliant with, an International Standards Organization (ISO) interchange standard for non-sequential recording (NSR) of data, known as ISO 13346. UDF is the subset of ISO 13346 as defined by the Optical Storage Technology Association (OSTA), a non-profit association for promoting the use of writable optical technologies and products for storage of computer data and images. UDF is a versatile file system supporting a wide variety of media technologies, such as CD, DVD, MO, WORM, and magnetic disk. UDF also builds on top of the ISO 13346 standard adding support for sequential recording media such as CD-R.
UDF is principally utilized for optical storage media. A common property of optical storage devices when compared to fixed discs is that optical drives may have long seek times and relatively low throughputs. When only a few files are being located, these performance issues may be sufficiently small that the user experience is not poor. However, when performing some action that requires access to very many files, the user experience can be frustrating. For example, if a volume of conventional size is checked for errors (e.g., “chkdsk” or “fschk”), every file on the volume is accessed.